Measurements of surface seawater fCO(2) from volunteer commercial ships: Techniques and experiences from Skaugran

Chemical measurements made in the northern North Pacific from a commercial volunteer observing ship (VOS) program during March 1995-March 1998 are pre sented. Quasi-continuous measurements of the fugacity of CO2 (fCO(2), which takes into account the nonideal nature of the gas; the values are within 0 .5-1.5 mu atm of the partial pressure in surface water) in seawater were ma de from two independent systems with different designs, and those results a re emphasized here. One system used a fast response bubbling equilibrator w ith measurements each minute; the other system used a showerhead equilibrat or with hourly measurements. Comparison of the results from these side-by-s ide systems provides useful information about the requirements for making h igh quality measurements of surface seawater and atmospheric fCO(2). From t his comparison, the fast response system is deemed to be more stable and po tentially more accurate. The utility of this system in waters with high spa tial variability is also demonstrated. Factors contributing to the success of this ship-of-opportunity program are discussed as a guidepost for future observing programs.